Various proof schemes, employed in blockchains' consensus protocols, necessitate different trust assumptions, and equivalently, offer different levels of digital trust to the ecosystems they are embedded in. If one imagines proof schemes on a scale for their provision of trust, Proof-of-Work (PoW) blockchains reside on one extreme, since they assume no preliminary digital trust, and provide all the digital trust needed via their operation. For this reason they are referred to as trustless computation environments, in the sense that no prior trust is needed among the users to be involved in the operation of the ecosystem. Initial blockchains such as Bitcoin [1]} and Ethereum [2]} employ PoW based consensus protocols.
